Quantification of myocardial blood flow with 82Rb dynamic PET imaging

Purpose The PET tracer Rb-82 is commonly used to evaluate regional perfusion defects for the diagnosis of coronary artery disease. There is limited information on the quantification of myocardial blood flow and flow reserve with this tracer. The goal of this study was to investigate the use of a one-compartment model of Rb-82 kinetics for the quantification of myocardial blood flow. Methods Fourteen healthy volunteers underwent rest and dipyridamole stress imaging with both N-13-ammonia and Rb-82 within a 2-week interval. Myocardial blood flow was estimated from the time-activity curves measured with N-13-ammonia using a standard two-compartment model. The uptake parameter of the one-compartment model was estimated from the time-activity curves measured with Rb-82. To describe the relationship between myocardial blood flow and the uptake parameter, a nonlinear extraction function was fitted to the data. This function was then used to convert estimates of the uptake parameter to flow estimates. The extraction function was validated with an independent data set obtained from 13 subjects with documented evidence of coronary artery disease (CAD). Results The one-compartment model described 82Rb kinetics very well (median R-square=0.98). The flow estimates obtained with Rb-82 were well correlated with those obtained with N-13-ammonia (r=0.85), and the best-fit line did not differ significantly from the identity line. Data obtained from the subjects with CAD confirmed the validity of the estimated extraction function. Conclusion It is possible to obtain accurate estimates of myocardial blood flow and flow reserve with a one-compartment model of Rb-82 kinetics and a nonlinear extraction function.